The
circuit of us do not work. We can check other devices by the meter. But the crystal will know how good or bad. Important point, the Crystal is expensive and time consuming to buy new. To buy a lot of inventory it is not worth, because we not often to use it. So we had better create a crystal tester circuit.
When the switch S1 is pressed to the
circuit, the current from the battery (B1-9 volt) to flow into circuit, the oscillated signal from emitter pin (E) of Q1 pass through to C4.
Circuit Crystal Tester BC107
The oscillator signal will be changing all the time, need to smooth with D1 and D2. Then, the signal is passed to the C5, which helps smooth up. At C5 has voltage across it, is a positive voltage to trigger a bias current to the Q2 works, as a result the
LED1 lights. The R3 limits the current through the LED1 to a value not exceeding 20 mA. If more than this, LED lights too, and short lived to LED1.
This project use equipment less. Therefore can be soldered onto the perforated board, easy to save money and time.